Mapping accuracy

The current hubbub about maps on the new version iOS has reminded me of a fascinating conversation I had a few years ago whilst doing a bit of work with the UK’s public mapping authority, Ordnance Survey.

OS produced quite a bit of revenue at the time from digital mapping products, often sold to major power and telecoms utilities to be able to help those customers provide geo-spatial data into their backend systems. Unfortunately, the advent of increased mapping accuracy as a result of GPS surveying techniques was starting to cause problems.

In the days before GPS, mapping was done through the triangulation of points on the ground. In densely-packed urban and even suburban areas this was fairly accurate, and the GPS-derived newer datasets worked fine. In rural areas, however, there was a problem. Triangulation wasn’t that accurate, so co-ordinates for something like a power line buried under a field could vary by a number of metres. If you were trying to dig up that power line, it could be a major issue. As a result, many of the utilities were at the time sticking with old datasets that were able to map their resources precisely, if not accurately.

Just goes to show that sometimes “the truth” isn’t necessarily what people really need…

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